chaseincats

UPDATE: I spoke with my old Z mechanic to see where he got the OEM thermostat that was in the car before my changeover to the new aftermarket one earlier this year since OEM ones are supposedly NLA. It turns out Nissan still makes a thermostat that works but is not the original one designated for the car. This thermostat is a Nissan part (part number 21200-F3190) but works in a bunch of their engines (L-series included). This is the thermostat that held the car's temperature at 170 from 2015-2020 before I started having cooling issues. I threw the old and new OEM thermostats as well as the aftermarket one in a pot of water. The old OEM thermostat started opening at 185 (unlike the new OEM one which opened around 170) and after continuing to heat the pot, the old OEM thermostat only ended up opening about 2/3's as much as the new OEM thermostat so the old OEM thermostat was indeed bad. The aftermarket one opened and closed at the same temperatures as the new OEM thermostat but the opening indeed is about 30% smaller than the OEM thermostat and the amount of travel the plunger can physically move is again maybe 30% less due to it being physically shorter. I have not tried the new thermostat in the car because driving it around in this cold weather won't give me a definitive answer, but I am feeling confident that my old worn-out OEM thermostat not opening at the right temperature (and not to the right amount) started this issue, and installing an aftermarket thermostat that physically can't move as much coolant as an OEM one kept me heating up, but for for a different reason entirely. With the new OEM thermostat correcting both issues, we should be all set come spring time. Here are pictures of the OEM one (right side) next to the aftermarket one (left side). You can see the opening is considerably smaller and plunger's travel is considerably shorter on the aftermarket unit. I will update you guys in the spring. I don't understand how/why they sell this design...

I've been asking in a variety of ways if the spacer is needed to have the gap between the body and tire identical on the front or rear. I haven't received a yes or no yet.

Oh, so the spacer would be necessary for the car's rear not to sag then it seems?

I haven't actually. That said, I have the considerably lighter (23 lbs) 77/78 bumpers so I don't think it would change the ride height as much as it would have with the 74-76 ones which were ~90 lbs each.

Any idea without the spacer, would the vehicle sit level with the ground or would the rear sag compared to the front?

Sorry if I'm not explaining my question well. What I am asking is if I put 4 of the standard strut mount insulators in and ignore their 260/280z-only rear insulator spacer (or any other donut/etc spacer) in there, will the rear wheel gap (good call on that metric) be greater than, less than, or equal to the wheel gap in the front?

It sounded like from your post/the fsm pic that adding their spacer to get back to 'stock' ride height for the 280 gave it a rake out of the factory where the body was higher in the back than the front and not using the spacer would get you/us a level-sitting car, no?

Gotcha, so in this case, to have a level car like a 240/260/any other car, the spacer isn't needed.

Since they increased the ride height on the rear of the car for the 280 means that when it was sold new it had a bit of a rake to it where the rear was higher than the front then?

Hi guys, I was reading that the 280z's rear strut mount was higher than teh 240's and requires a spacer (this part). If I don't add this to the car, does that mean the front will sit higher than the rear or did the 280z have a rake to it when new?

Good catch, I should have added that I did pressure test the cooling system and radiator cap when I installed all of that new hardware a few months ago. I also did a leak-down test yesterday and besides finding out I have a few tired piston rings, I confirmed there isn't any combustion gas leaking into the coolant.

The car has a new radiator and water pump and before I did that, I flushed out the rust (in theory) with the radiator flush chemical a few times and did the old 'hose in the thermostat housing' routine.

I've heard from a bunch of sources that the smaller opening of the aftermarket thermostats compared to the OEM one (and apparently now this) hinders cooling. That's the case at least (probably) on my car.

I'll give that a shot, thanks! Has anyone tried this thermostat in a world where the OEM one is NLA?

Update for you guys. I spoke with my old Z mechanic and he said (and I've heard from a couple folks on Z forums too) that aftermarket thermostats don't flow as much coolant as an OEM one. Has anyone else here heard of this or is it more of a wives tale? I took my old Nissan OEM thermostat and popped it in a pot of water and the 170 degree thermostat didn't start opening until 185ish so I'm guessing that was bad and the new one which is aftermarket isn't large enough to flow enough coolant for a steady temp. Can anyone recommend a 170 degree thermostat that flows as much coolant as an OEM one? Currently the thermostat I have is this.

Hi all - Wondering if anyone knows where the fuel pump ground wire terminates in the car. The pump has two wires going into the wiring loom but the service manual says one of them terminates directly to a ground. Any idea where that hides on a 1978?

Hi all, I just put a Dynomax SuperTurbo 17733 on my stock 280 and it is noticeably quieter than the (what turned out to be magnaflow) muffler that was sawed off. I took a look under the car (no cat) and I believe the below is a resonator (correct me if I'm wrong). Do these need to be removed when using the SuperTurbo muffler? The car is almost EV quiet after swapping the magnaflow with this.

Gotcha, so I shouldn't expect the temp to drop if I do that then? Yep, I have the shroud

drops back to operating temp

Heater is good. I do have an aftermarket thermostat installed not OEM Nissan if that matters. The original thermostat I had in there was OEM but the overheating issue also happened with that in there. Next time I drive the car and it heats up I'll raise the idle and see what happens but either way that should test airflow and coolant flow since it would be spinning the pump and fan faster, right?

When this whole thing started I changed the fan clutch, radiator (kept the fan shroud), water pump, thermostat, and used radiator flush so it shouldn't be any of those components...

Update on this. I noticed the car is now only heating up after getting to operating temperature and then driving slowly/idling. Once the car is driving, the temperature drops like a stone which kills my theory about combustion gas in the coolant. They car will puff some white (not blue) smoke when changing gear under WOT so I'm guessing that means the gasket is somewhat compromised in the coolant passages anyway. The car has a brand new Aisin fan clutch which had the same warming-up issue that developed with the old fan clutch which was in good condition anyway. I checked the fan belt's tension and it was good as-is too. Any other ideas?

Update on this. I noticed a few weeks ago that the temp gauge briefly rises when I really hit the pedal and will fall when I drop the idle. That lead me to believe theres combustion gas sneaking into the coolant. Following the directions, I siphoned out a few inches of coolant from the radiator and after about 20 seconds of pumping, the squeeze pump stopped expanding because I was probably pulling coolant into the tester at that point. Because of this, I was unable to do a full 2 minute squeeze test. My question is, can I squeeze the pump until its hard to squeeze, pop it out of the radiator to drop the coolant level back down (now that its no longer under vacuum from the bottle) so I can keep squeezing (as long as I dont squeeze the bulb when I pop it out) or will that contaminate the test? EDIT: I grabbed my transfer pump and sucked enough coolant out of the radiator to fill my overflow bottle (it was about 1/8 full). That gave me more air to pump out of the rad and the color didn't change. My only guess at this point is the leak in the head/head gasket (if that's the issue) is so small that the only time it gets enough gas to heat the car up is when theres more pressure in the cylinders due to higher rpm. I think the plan will be to just drive it until it's bad enough that it heats up at idle and try the test again.

The main efi relay had some resistance so maybe the efi system wasnt getting full power? My main guess is the fuel pump relay had resistance, so maybe it took a little bit longer for power to push its way through the corrosion to turn the pump on? Who knows - all I do know is everyone should test the relays for resistance. The only reason I resurected this old thread was for that PSA haha

I cleaned 2 things - 1) the "teeth" that sit outside of the relay housing (the things that plug into the harness). After cleaning the teeth I took resistance measurements between the circuits. For example (I didn't need to clean this one but it's easy to explain this way) - the fuel pump control relay has 4 teeth. By activating the relay by touching a 9v battery to the left 2 of the 4 teeth the relay will click, I then measured the resistance of the high power circuit (the side which is actuated by the relay itself) 2) if resistance is found (anything over 0.02ish on the multimeter's ohm setting), I opened up the relay by bending the locking prongs back to pull the top of it off. Once open you'll see 2 contacts and rocker looking like this: \ |/ when actuated, the relay arm will shift to \| /. For relays that had resistance, there ALWAYS was some sort of black marks either on the contact side \ / or the relay rocker arm side | Using sandpaper i cleaned them all up and took another measurement confirming there was no more resistance. Top tip: the screw at the bottom of each relay has nothing to do with opening the casing, it screws the relay electrics to the bottom plastic base. Unscrew that screw to pull the articulating arms out of the contacts, it makes it WAY easier to clean both sides that way and screws back in easily.